Spring valve implemented flow control valves

ABSTRACT

Improved low flow impedance flow control valves are disclosed in the present invention wherein spring valve means ( 12 ) captured between a valve spool ( 28 ) and a shoulder ( 30 ) are utilized for selectively metering a flow of fluid from an inlet port ( 18 ) to an outlet port ( 14 ) via a round edged helical orifice ( 82 ) formed between the open coils of the spring valve ( 12 ) as a function of the instant axial position of the valve spool ( 28 ) and the differential pressure therebetween. An improved method of controlling low impedance flow control valves is also disclosed in the present invention. The improved method provides better accuracy in controlling fluid flow through low flow impedance flow control valves through continually cycling a means for substantially interrupting fluid flow therethrough in a low frequency pulse width modulated fashion.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to hydraulic valves, andmore particularly to improved low flow impedance two- and three-way flowcontrol valves, wherein such two- and three-way flow control valves areoptimized for controlling automotive engine heated coolant flow to ahost vehicle's radiator, or between the radiator and a bypass line, oreven to its heater core.

[0003] 2. Description of the Prior Art

[0004] Flow control valves optimized for operation under conditions oflow flow impedance are known in the prior art. One such prior artthree-way flow control valve is manufactured by Spartan PeripheralDevices of Vaudreuil, Quebec, Canada. This three-way flow control valvehas an axially oriented inlet port and first and second radiallyoriented output ports. It has a valve spool configured in a generallyround thin walled cylindrical manner and has a central web forstructural stability and connection to a valve stem. The valve spool isconfigured with a round outer periphery terminated by first and secondorthogonal ends that serve as metering edges.

[0005] Fluid conveyed from the inlet port to the first output portmerely passes through a first annular orifice formed between the firstorthogonal end and a first bulkhead formed as part of an input fitting.On the other hand, fluid conveyed from the inlet port to the secondoutput port must first pass through the valve spool itself and then passthrough a second annular orifice formed between the second orthogonalend and a second bulkhead formed as part of a bonnet. For this reason,the valve spool is formed with an internal flow channel between spokesof a web for conveying fluid from a first chamber formed within thefirst end to a second chamber formed within the second end.

[0006] The valve spool is slidingly located within a bore of minimallength locateded in a third bulkhead formed in the housing forseparating the first and second output ports. The valve spool ispositioned axially by a valve stem. The valve stem is mounted within abore formed concentrically within the central web thereby forming ametering assembly comprising the valve spool and valve stem. Inaddition, the valve stem is slidingly located within a bore locatedconcentrically within the bonnet. Thus, the metering assembly isprovided with orthogonal radial position constraints at each of thefirst bulkhead formed in the housing and second bulkhead formed in thebonnet. A fifth positional constraint is provided by the axialpositioning of the metering assembly itself while the sixth orrotational constraint about the axis of motion of the metering assemblyis not required for proper functioning of the three-way valve.

[0007] Another prior art low flow impedance three-way flow control valveis disclosed in my Provisional U.S. patent application Ser. No.60/220,340 filed on Jul. 24, 2000 and entitled “Three-Way Flow ControlValve Having Low flow Impedance”. The '340 application discusses a lowimpedance three-way flow control valve utilized for controlling enginecoolant flow between a radiator and a bypass line. In the low impedancethree-way flow control valve disclosed in patent application '340, avalve spool apportions fluid flow between axially offset first andsecond flow receiving annular passages from a central flow distributionchamber. Similarly to the prior art three-way valve described above, thethree-way flow control valve disclosed in patent application '340 isconfigured with an axially oriented inlet port and first and secondoutput ports. However, in the three-way flow control valve disclosed inpatent application '340, axially offset first and second flow receivingannular passages are respectively formed as inner portions of the firstand second output ports. Further, the housing of the three-way flowcontrol valve disclosed in patent application '340 is formed with itsinternal bore extending through sealing bulkheads formed on either sideof the axially offset first and second flow receiving annular passagesas well as a central housing bulkhead.

[0008] One negative aspect of either valve construction is practicaldifficulty in operating their valves with a proportional solenoid.Through extensive testing of the flow control valve disclosed in patentapplication '340, it has been found that impurities commonly found inautomotive engine heated coolant tend to interfere with smooth operationof any juxtaposed sliding surfaces such as those found in anyconventional valve or solenoid. This factor appeared to substantiallydoom the general concept of providing proportional solenoid controlledlow flow impedance flow control valves unless a way of eliminating suchjuxtaposed sliding surfaces could be provided through implementation ofimproved low flow impedance flow control valves.

[0009] Further, It has also been found that the relatively high rate offluid flow itself tends to interfere with maintenance of an axial forcebalance on the valve spool. This is because of the formation of venacontractas located slightly downstream of each of the annular orifices.As the axial position of the valve spool and/or the output portpressures vary, reaction forces generated by the vena contractas vary aswell. This results in net axial force values being applied to the valvespool. In addition, the presence of the vena contractas means that theeffective areas of the first and second annular orifices aresignificantly less than the apparent annular areas formed by the gaps ateither end of the valve spool. The combination of these factors resultsin a requirement for a much stronger proportional solenoid having anapproximately 50% longer stroke length than would be the case if a wayof eliminating such vena contracta formation could be found forutilization in the improved low flow impedance flow control valves.

[0010] In addition, it has been found difficult to reliably regulatedifferential fluid flow between the radiator and bypass line as afunction of valve spool position. This is because the flow impedance ofeach of the first and second annular orifices is similar to or evenlower than the load impedance presented by either the radiator or thebypass line.

[0011] It would be advantageous to provide method and apparatus forcontrolling engine coolant flow between a radiator and bypass line whereno vena contractas are formed with reference to flow control orificesand no juxtaposed sliding surfaces are exposed to engine heated coolant,and further, to provide a method of operation whereby engine coolantflow between the radiator and the bypass line is reliably regulated.

SUMMARY OF THE INVENTION

[0012] These and other objects are achieved in improved two- andthree-way low flow impedance flow control valves according to thepresent invention, in which axially moving valve spools are supported byrolling diaphragms and actuate one or more spring valves formedgenerally in the manner of compression springs. The valve spools areutilized for axially positioning the inner end or ends of one or morespring valves with reference to a fixedly located opposite end or endsthereof, thereby apportioning fluid flow via one or more round edgedhelical orifices formed between individual spring coils amongst a likenumber of flow receiving generally annular chambers from a central flowdistribution chamber or chambers.

[0013] Similarly to the prior art three-way valves, the two-way and afirst type of three-way valve of the present invention are configuredwith an axially oriented inlet port and one or more radially orientedoutput passages leading to an output port or respective output ports. Inaddition, that three-way valve has a flow channel formed in its valvespool for conveying fluid flow from its inlet port and a first centralflow distribution chamber formed within the first spring valve to asecond central flow distribution chamber formed within the second springvalve.

[0014] In any of the flow control valves of the present invention, flowcontrol is obtained by moving their valve spools axially thereby openingand/or closing the round edged helical spaces between the coils of thespring valves to form the round edged helical orifices. In the case ofthe three-way valves, the extent of valve stroke excursion is controlledby closure of either of the first and second spring valves while in thecase of a two-way valve having only one spring valve, the extent ofvalve stroke excursion in one direction is controlled by closurethereof.

[0015] In the case of such a two-way valve, the rolling diaphragm usedfor supporting the valve spool is also utilized for fluidly isolating aback chamber located behind the valve spool from either of the radiallyoriented output passage and the outside environment. Pressure values oneither side of the valve spool are balanced via a pressure balancingport formed in the valve spool. In order to substantially keepimpurities out of the back chamber; a suitable filter is mounted in thepressure balancing port.

[0016] As in the prior art three-way valves, a proportional solenoid canbe utilized for positioning the valve spools of the two- and three-wayvalves of the present invention. In order to prevent contaminationhowever, the plunger cartridge is isolated from the back chamber by adifferential rolling diaphragm.

[0017] In such proportional solenoid activated two- and three-wayvalves, spring valve generated force urges the valve spool towards theplunger and is opposed by force provided by the proportional solenoid.Thus, there is an abutting interface between plunger and valve spoolwhereby the plunger is enabled for positioning the valve spool. Forconvenience in compensating for practical manufacturing tolerances,means for fixedly locating the opposite end of the spring valve comprisean axially adjustable ring. The axially adjustable ring is positionedsuch that the round edged helical orifice of the spring valve issubstantially closed when the proportional solenoid is nominally at itsfully energized travel limit.

[0018] Improved low flow impedance two-way flow control valves may beutilized to replace the normally utilized thermostat in an intelligentcooling system, for a radiator bypass line leading directly back to theinlet port of the host cooling system's pump, and/or even forselectively distributing engine coolant flow to a heater core. In thecase of the replacement of a thermostat, the engine cooling function isrendered inherently fail-safe as follows: Should the solenoid or itsdrive fail, the plunger would be driven back by the spring valve wherebythe spring valve will be rendered fully open. Thus, in case of such afailure all coolant would be directed to the radiator.

[0019] In the case of a three-way valve activated by a proportionalsolenoid, the valve housing is formed with a central housing bulkheadseparating first and second radially oriented output passages. A rollingdiaphragm is used for supporting the valve spool and for fluidlyisolating the first and second radially oriented output passages onefrom another. The first spring valve of the three-way valve isconfigured with stronger compression force than the second spring valvewhereby the difference in compression forces between the first andsecond spring valves urges the valve stem and spool towards its plunger.Thus, there is an abutting interface between plunger and valve stemwhereby the plunger is enabled for positioning the valve spool in themanner described above.

[0020] An axially adjustable ring is used for fixedly locating theopposite end of the first spring valve. In this case however, theaxially adjustable ring is positioned such that a selected sum of axialopening values of the first and second round edged helical orifices isachieved. The valve stem is threadably attached to the valve spoolwhereby the valve stem is relatively positioned such that the roundedged helical orifice of the first spring valve is substantially closedwhen the proportional solenoid is fully energized.

[0021] The improved low flow impedance three-way flow control valve isprimarily intended for use in a highly sophisticated intelligent coolingsystem wherein engine coolant flow is selectively distributed between aradiator line leading to the input fitting on the host vehicle'sradiator, and a radiator bypass line leading to a centrifugal pump inletwherein the radiator line is connected to a first port and the radiatorbypass line is connected to a second port. This arrangement is preferredbecause it is inherently fail-safe. Should the solenoid or its drivefail, the stronger first spring valve would fully open and drive thesecond spring valve closed along with the plunger. Thus, in case of sucha failure all coolant would be directed to the radiator.

[0022] Interestingly, in the case of a two-way valve utilized inconjunction with a radiator bypass line the above-described fail-safefunction must be inverted. Generally such a radiator bypass line is usedin conjunction with a two-way valve controlling coolant flow to a hostvehicle's radiator. As already described, the proper failsafe conditionis for all coolant to flow through the radiator whereby it is clear thatthe fail-safe condition for the two-way valve utilized in conjunctionwith a radiator bypass line is for that valve to close rather than open.Such a two-way valve could be termed a normally closed two-way valve. Inany case, this problem is readily solved by utilizing the improved lowflow impedance three-way valve with output flow from its first radiallyoriented output passage blocked by the simple expedient of not providinga first output port. Then the fail-safe condition is implemented bystopping electrical current flow to the proportional solenoid.

[0023] The valve spools utilized in the flow control valves of thepresent invention avoid the deleterious effects of Coulomb frictionprimarily because they are located by rolling diaphragms. Further, thespring valves effect flow metering via closure of the round edgedhelical orifices rather than via closure of sharp edged orifices. As aresult, no vena contractas are formed with respect to fluid flow throughthe round edged helical orifices. This results in minimal stroke lengthand absence of unwanted axial force components for the spring valves.These factors combine to result in minimal size and drive power for theproportional solenoids. Further, because of the lack of Coulomb frictionit is possible to control valve spool displacement without positionfeedback.

[0024] These factors have in part been enabled by a new method ofselective flow metering via closure of round edged helical orificesformed between coils of spring valves comprising: providing a fluid flowpath wherein substantially all fluid to be selectively metered flowsradially through a round edged helical orifice formed between coils of aspring valve; and reducing or increasing the size of that round edgedhelical orifice by respectively compressing or allowing axial expansionof the spring valve.

[0025] As mentioned above however, it has been found difficult toreliably regulate differential fluid flow between the radiator andradiator bypass line as a function of valve spool position. Again, thisis because the flow impedance of each of the first and second annularorifices is similar to the load impedance presented by either of theradiator or bypass lines. In addition, it may prove necessary toperiodically clear debris from the round edged helical orifices.

[0026] Both of these problems can easily be resolved according to a newmethod of operating any of the improved low flow impedance flow controlvalves as a “bang-bang” servo wherein in the case of a flow controlvalve comprising a single orifice that orifice is continually cycledbetween fully open and closed positions in low frequency pulse widthmodulated fashion, or in the case of a flow control valve comprisingmore than one orifice those orifices are alternately continually cycledbetween fully open and closed positions in low frequency pulse widthmodulated fashion. In the later case for instance, the regulation ofdifferential fluid flow between the radiator and radiator bypass linevia the improved low flow impedance three-way flow control valve isaccomplished by directly controlling the fraction of time when allengine coolant flow passes through the radiator vs. the remainingfraction of time when all engine coolant flow passes through theradiator bypass line.

[0027] In general, the new method of controlling low impedance flowcontrol valves comprises: providing at least one interruptible fluidflow path between a source and a selectable destination of fluid flow;providing means for substantially interrupting fluid flow through asingle such fluid flow path, or alternately through either of multiplesuch fluid flow paths; and continually cycling the means forsubstantially interrupting fluid flow in a low frequency pulse widthmodulated fashion.

[0028] Traditional in-line design has been implied in the so fardescribed improved low flow impedance two-and three-way flow controlvalves. However, this is by no means a requirement for implementing thenew method of selective flow metering. Because of the self-centeringnature of spring valves it is possible to utilize a pair of levercoupled and oppositely directed two-way spring valves in implementing afurther simplified second type of low flow impedance three-way flowcontrol valve. To differentiate it from the first type thereof, it willbe termed a three-way flow control valve assembly hereinafter. Similarlyto the first type of three-way flow control valve, a first outputpassage fluidly communicates with a radiator input line while a secondoutput passage fluidly communicates with a radiator bypass line.

[0029] The bang-bang servo mode of control is utilized in the three-wayflow control valve assembly thereby obviating any requirement for aproportional or push-type solenoid. A standard pull-type solenoid isquite suitable. These factors are utilized advantageously hereinbelow inimplementing a low flow impedance three-way flow control valve assemblythat is fully integrated together with a centrifugal pump within acommon housing that can, if desired, be directly mounted on anautomotive engine.

[0030] A pair of two-way spring valves is radially disposed withreference to a single central flow distribution port in the three-wayflow control valve assembly. The individual two-way spring valvesfunction generally as poppet valves in selectively controlling enginecoolant flow to first and second generally annular passages respectivelyfluidly coupled to the radiator input and radiator bypass linesmentioned above. Each of their valve heads is sealed by a rollingdiaphragm. As in the three-way valve previously described, the first oneof the two-way spring valves utilizes a stronger spring than the secondone so that the fail safe mode results in all coolant flow going to theradiator. The valve heads are axially located by cam followers mountedon a lever. The lever is actuated by a simple linkage-coupled pull-typesolenoid against the differential force provided by the springs.

[0031] The radiator bypass line is implemented as a bypass passage thatdirectly fluidly couples the second generally annularly oriented outputchamber of the three-way flow control valve assembly with an inputchamber of the centrifugal pump. The centrifugal pump can be driveneither by the engine's accessory drive belt or by an electric motor, andis used to drive coolant through the engine's coolant passages and thecoolant system as a whole. The three-way flow control valve assembly isused to selectively divide coolant flow issuing from the engine coolantpassages between the radiator input line and the bypass passage.

[0032] In passing it is worth noting that it would also be possible toimplement an alternate low flow impedance three-way flow control valveassembly generally constructed according to the above describedarchitecture wherein the spring. valves are replaced by mechanicalmetering edges. In this case the valve heads are formed with orthogonalends that serve directly as the metering edges. Further, the valve headsare fixedly attached to the lever, which lever acts against a dedicatedreturn spring utilized for urging the valve heads and solenoid plungertoward their fail safe positions.

[0033] In a first aspect, then, the present invention is directed to animproved low flow impedance two-way flow control valve of the typehaving a housing; an axially oriented inlet port located within a firstend of the housing; an annularly oriented radial output passage disposedwithin the housing proximate to its first end; and an axially movingvalve spool, wherein the improvement comprises: a rolling diaphragmlocated proximate to the second end of the housing for fluidly isolatingthe annularly oriented radial output passage from a back chamber formedbehind the valve spool and constraining the valve spool for axialmovement within the housing; and spring valve means captured between thevalve spool and a shoulder located within the first end of the housingfor selectively metering a flow of fluid from the inlet port to theoutput passage via a round edged helical orifice formed between the opencoils of the spring valve as a function of the instant axial position ofthe valve spool and the differential pressure therebetween.

[0034] In a second aspect, the present invention is directed to aparticular combination of the elements identified above. Moreparticularly in this second aspect, the present invention is directed tothe improved low flow impedance two-way flow control valve of the firstaspect additionally comprising: a proportional solenoid for axiallypositioning the valve spool via a push type plunger thereof; a pressurebalancing port formed in the valve spool for conveying fluid from theinlet port to the otherwise nominally sealed back chamber for balancingfluid pressure values on either side of the valve spool; a filtermounted in the pressure balancing port for substantially keepingimpurities out of the back chamber; a differential rolling diaphragmlocated proximate to the proportional solenoid for fluidly isolating theplunger cartridge of the proportional solenoid from any possiblecontamination by coolant present within the back chamber; and furtherwherein the shoulder is configured as part of an axially adjustable ringfor positioning the shoulder such that the round edged helical orificeof the spring valve is substantially closed when the proportionalsolenoid is fully energized thereby positioning the plunger at itsnominal travel limit.

[0035] In a third aspect, the present invention is directed to animproved low flow impedance three-way flow control valve of the typehaving a housing; an axially oriented inlet port located in a first endof the housing; first and second annularly oriented radial outputpassages disposed within the housing and fluidly isolated one fromanother by a central housing bulkhead, the first annularly orientedradial output passage being located proximate to a first end of thehousing and the second annularly oriented radial output passage beinglocated proximate to the second end of the housing; and an axiallymoving valve spool, the valve spool being positioned by a valve stem andincluding an axially oriented flow channel, wherein the improvementcomprises: a rolling diaphragm located proximate to the central housingbulkhead for fluidly isolating the radially oriented output passages onefrom another and constraining the valve spool for axial movement withinthe housing; first spring valve means captured between the valve spooland a shoulder located within the first end of the housing forselectively metering a flow of fluid from the inlet port to the firstoutput passage via a round edged helical orifice formed between the opencoils of the first spring valve as a function of the instant axialposition of the valve spool and the differential pressure therebetween;and second spring valve means captured between the valve spool and thesecond end of the housing for selectively metering a flow of fluid fromthe inlet port to the second output passage via the flow channel and around edged helical orifice formed between the open coils of the secondspring valve as a function of the instant axial position of the valvespool and the differential pressure therebetween.

[0036] In a fourth aspect, the present invention is directed to aparticular combination of the elements identified above. Moreparticularly in this fourth aspect, the present invention is directed tothe improved low flow impedance three-way flow control valve of thethird aspect additionally comprising: a proportional solenoid foraxially positioning the valve stem and valve spool via a push typeplunger thereof; the first spring valve means being configured withstronger compression force than the second spring valve means for urgingthe valve stem and valve spool towards the plunger; a differentialrolling diaphragm located proximate to the proportional solenoid forfluidly isolating the plunger cartridge of the proportional solenoidfrom engine heated coolant generally present within the two-way flowcontrol valve; the shoulder being configured as part of an axiallyadjustable ring for positioning the shoulder such that a selected sum ofaxial opening values of the first and second round edged helicalorifices is achieved; and means for adjustably attaching the valve stemto the valve spool for relative axial positioning thereof after theaxially adjustable ring has been properly positioned, such that theround edged helical orifice of the first spring valve is substantiallyclosed when the proportional solenoid is fully energized therebypositioning the plunger at its nominal travel limit.

[0037] In a fifth aspect, the present invention is directed to aparticular combination of the elements identified above. Moreparticularly in this fifth aspect, the present invention is directed tothe improved low flow impedance three-way flow control valve of thethird aspect modified by blocking output flow from its first radiallyoriented output passage via the simple expedient of not providing anoutput port therefore so as to reconfigure the improved low flowimpedance three-way flow control valve as a normally closed two-wayvalve.

[0038] In a sixth aspect, the present invention is directed to a newmethod for selective flow metering comprising the steps of: providing afluid flow path wherein substantially all fluid to be selectivelymetered flows radially through a round edged helical orifice formedbetween coils of a spring valve; and reducing or increasing the size ofthat round edged helical orifice by respectively compressing or allowingaxial expansion of the spring valve.

[0039] In a seventh aspect, the present invention is directed to a newmethod for controlling low impedance flow control valves comprising:providing at least one interruptible fluid flow path between a sourceand a selectable destination of fluid flow; providing means forsubstantially interrupting fluid flow through a single such fluid flowpath or alternately through either of multiple such fluid flow paths;and continually cycling the means for substantially interrupting fluidflow in low frequency pulse width modulated fashion.

[0040] In an eighth aspect, the present invention is directed to animproved low flow impedance three-way flow control valve assemblycomprising: first and second coupled and oppositely directed two-wayvalves; respective first and second generally annularly oriented outputpassages for receiving selectively apportioned engine coolant flow fromthe first and second two-way valves; a lever for mechanically couplingand physically driving the first and second two-way valves; and meansfor mechanically driving the lever.

[0041] In a ninth aspect, the present invention is directed to aparticular combination of the elements identified above. Moreparticularly in this ninth aspect, the present invention is directed tothe improved low flow impedance three-way flow control valve of theeighth aspect, additionally comprising: two-way spring valves utilizedfor the first and second coupled and oppositely directed two-way valves;a pull-type solenoid utilized as the means for mechanically driving:respective first and second valve heads for actuating the springscomprised in the spring valves; and respective first and second rollingdiaphragms for fluidly isolating the lever and pull-type solenoid fromthe engine coolant.

[0042] In a tenth aspect, the present invention is directed to aparticular combination of the elements identified above. Moreparticularly in this tenth aspect, the present invention is directed tothe improved low flow impedance three-way flow control valve of theeighth aspect, additionally comprising: mechanical metering edgesutilized for the first and second coupled and oppositely directedtwo-way valves; a pull-type solenoid utilized as the means formechanically driving: respective first and second valve headsmechanically coupled to the lever and comprising the mechanical meteringedges; and respective first and second rolling diaphragms for fluidlyisolating the lever and pull-type solenoid from the engine coolant.

[0043] In an eleventh and final aspect, the present invention isdirected to a fully integrated pump-valve assembly comprising the lowflow impedance three-way flow control valve assembly of the eighthaspect, and additionally comprising a centrifugal pump, wherein thevalve assembly and its associated flow passages are housed and includedalong with the centrifugal pump and a bypass passage for fluidlycoupling the second generally annularly oriented output passage of thethree-way flow control valve assembly with an input chamber of thecentrifugal pump within a common housing that can be directly mounted onan automotive engine.

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] A better understanding of the present invention will now be hadwith reference to the accompanying drawing, wherein like referencecharacters refer to like parts throughout the several views herein, andin which:

[0045]FIG. 1 is a partially schematic sectional view of an improved lowflow impedance two-way flow control valve of the present invention;

[0046]FIGS. 2A and 2B are partially schematic sectional views of animproved low flow impedance three-way flow control valve of the presentinvention;

[0047]FIG. 3 is a plan view of the three-way flow control valve of thepresent invention;

[0048]FIG. 4 is a partially schematic sectional view of a normallyclosed low flow impedance two-way flow control valve of the presentinvention;

[0049]FIG. 5 is a flow chart depicting a method for adjustably varyingfluid flow through the low flow impedance valves of the presentinvention;

[0050]FIG. 6 is a flow chart depicting a method for operation of any ofthe improved low flow impedance flow control valves of the presentinvention in the manner of a “bang-bang” servo;

[0051]FIG. 7 is a schematic diagram illustrating a circuit useful inimplementing the method of FIG. 6;

[0052]FIG. 8 is a sectional view of an improved low flow impedancethree-way flow control valve assembly of the present invention;

[0053]FIG. 9 is a partially schematic isometric view of the improved lowflow impedance three-way flow control valve assembly shown in FIG. 8;and

[0054]FIG. 10 is a sectional view of an improved low flow impedancethree-way flow control valve assembly of the present invention whereinspring valves have been replaced by mechanical metering edges.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0055] With reference now to FIG. 1, thereshown in a partially schematicsectional view is improved low flow impedance two-way flow control valve10. In the two-way flow control valve 10 a spring valve 12 havingsquared and ground ends apportions fluid flow to an annularly orientedradial output passage 14 from a central flow distribution chamber 16.Incoming fluid is provided directly to the flow distribution chamber 16from an axially oriented inlet port 18 formed at a first end 20 ofhousing 22 while a flow of output fluid is disbursed from an output port24 fluidly communicating with the annularly oriented radial outputpassage 14. The spring valve 12 is disposed between a shoulder 26 formedon the leading edge of a valve spool 28 and another shoulder 30 locatedwithin the inlet port 18. The valve spool 28 is driven in an axialdirection by the push type plunger 32 of a plunger cartridge 34comprised within a proportional solenoid 36. The plunger cartridge 34 isdirectly mounted in a back plate 38 (attached to the housing 22 viabolts—not shown) in a standard manner via a straight tube boss 40 whilea coil 42 is mounted upon the plunger cartridge 34 and then urged intocontact with the back plate 38 by a retaining nut 44.

[0056] The annularly oriented radial output passage 14 is fluidlyisolated from a back chamber 46 formed behind the valve spool 28 by arolling diaphragm 48. Pressure values on either side of the valve spool28 are balanced by a pressure balancing port 50 formed in the valvespool 28. In order to substantially keep impurities out of the backchamber 46; a filter 52 is mounted in the pressure balancing port 50.And in order to prevent any possible contamination by the coolant, theplunger cartridge 34 is isolated from the back chamber 46 by adifferential rolling diaphragm 54.

[0057] The differential rolling diaphragm 54 comprises a nose plate 56formed from a rigid material for effectively conveying plungerdisplacement to a button 28btn formed on the valve spool 28. Immediatelysurrounding the nose plate 56 are first and second annular convolutions58 a and 58 b formed of an elastomeric material. This in effect formstwo concentric pistons respectively equal in diameter to the roots ofeither of the first and second annular convolutions 58 a and 58 b. Theconcept of the differential rolling diaphragm 54 is that whenever theplunger 32 moves, the first annular convolution 58 a and its effectivepiston is displaced as well. Then fluid on either side of thedifferential rolling diaphragm 54 is also displaced in such a manner asto displace the second annular convolution 58 b and its effective pistonin the opposite direction in a volumetrically equal manner such thatthere is substantially no pressure buildup within the plunger cartridge34. The outer periphery of the differential rolling diaphragm 54 isformed with an annular sealing ridge 60 disposed within an annular shell62. In assembly the annular sealing ridge 60 is compressed against arecessed face 64 of the back plate 38 by pressing a retaining ring 66commonly known as a circular push-on against the annular shell 62. Outerteeth formed on the retaining ring 66 then retain the outer periphery ofthe differential rolling diaphragm 54 against the recessed face 64 by aninterference fit with bore 68. Suitable circular push-on retaining ringsfor this purpose are available from Waldes Truarc of Millburn, N.J.

[0058] An inner annular bead 70 of the rolling diaphragm 48 is sealinglyafixed to the valve spool 28 via compression between valve spool body 28b and valve spool ring 28 r portions thereof during assembly. The valvespool ring 28 r is so retained on the valve spool body 28 b bydisplacing an annular protrusion 28 p against a conical surface 28 c ofthe valve spool ring 28 r. An outer annular bead 72 of the rollingdiaphragm 48 is sealingly trapped between an annular protruding ring 74formed on the back plate 38 and a shoulder 76 formed on the housing 22.Suitable rolling diaphragms for this purpose are available fromBellofram of Newell, W.V.

[0059] For convenience in compensating for practical manufacturingtolerances, the shoulder 30 is made axially adjustable by virtue ofbeing configured as the near end of an adjustment ring 78 threadinglyinserted in threads 80 formed in the housing 22. During assembly of theimproved two-way flow control valve 10, the proportional solenoid 36 isaxially positioned a selected small distance from its internal closedphysical stop (not shown) and the axial position of the adjustment ring78 is adjusted such that the round edged helical orifice 82 formedbetween the coils 84 of the spring valve 12 is nominally closed. Thenthe adjustment ring 78 is staked in position. Thus, the round edgedhelical orifice 82 can be modulated in size between a nominally closedvalue effected when the proportional solenoid 36 is fully energized, anda maximally open value as determined by solenoid stroke to its internalopen physical stop (also not shown) as energized by force provided bythe spring valve 12. Substantially force balanced operation is providedby selected values of plunger force opposed by compressive force fromthe spring valve 12 through its range of axial positions. In practicethis is accomplished by modulating electrical current flowing throughthe solenoid 36 according to known current to plunger force conversionvalues.

[0060] As depicted in the partially schematic sectional view presentedin FIG. 1, the improved low flow impedance two-way flow control valve 10of the present invention is primarily intended for use in selectivelyconveying engine coolant flow to a radiator 86 in place of a thermostatin an intelligent cooling system. Then an input line 88 returns thecoolant coming from the radiator 86 to the inlet port 90 of an enginedriven centrifugal pump 92. In addition, a bypass line 94 may beprovided for conveying a nominal amount of coolant directly to the inletport 90 without passing through the radiator 86. This may be necessaryin order to avoid hot spots when the improved low flow impedance two-wayflow control valve 10 is closed. In any case, coolant issuing fromoutput port (not shown) of the centrifugal pump 92 next flows throughengine 98 and is eventually returned to the inlet port 18 and the bypassline 94.

[0061] As implied above, the improved low flow impedance two-way flowcontrol valve 10 of the present invention could also be used forselectively conveying engine coolant flow to a heater core 100. In sucha case engine heated coolant is conveyed from the output port 24 to theheater core 100. To complete the heater coolant flow circuit, coolantissuing from the heater core 100 is returned to the inlet port 90 of thecentrifugal pump 92.

[0062] With reference now to FIGS. 2A, 2B and 3, thereshown in partiallyschematic sectional and plan views is improved low flow impedancethree-way flow control valve 110. In the improved three-way flow controlvalve 110, first and second spring valves 114 a and 114 b respectivelyapportion fluid flow to first and second annularly oriented radialoutput passages 116 a and 116 b via first and second round edged helicalorifices 118 a and 118 b from first and second central flow distributionchambers 120 a and 120 b defined in part by a valve spool 122. The firstand second annularly oriented radial output passages 116 a and 116 b arerespectively located proximate to first and second ends 134 and 112 ofhousing 126 and are physically separated one from another by a bulkhead124 formed therein. As in the two-way flow control valve 10, the valvespool 122 is radially located by the rolling diaphragm 48 utilized inthis case to provide fluid isolation between the first and secondannularly oriented radial output passages 116 a and 116 b. This time theouter periphery of the differential rolling diaphragm 48 is retained bya cylinder ring 125 and a circular push-on retaining ring 127 against ashoulder 129 formed in the bulkhead 124. The first and second annularlyoriented radial output passages 116 a and 116 b fluidly communicate withfirst and second output ports 128 a and 128 b, respectively, wherefromrespective first and second flows of output fluid are disbursed.

[0063] The valve spool 122 is utilized to differentially position theinner ends of the first and second spring valves 114 a and 114 b suchthat as either round edged helical orifice 118 a or 118 b opens theother closes. Incoming fluid is provided directly to the first flowdistribution chamber 120 a from an axially oriented inlet port 132formed at a first end 134 of the housing 126. Fluid is provided to thesecond flow distribution chamber 120 b from the first flow distributionchamber 120 a via a flow channel 136 comprising multiple passagesbetween individual spokes of a central web structure 138 of the valvespool 122.

[0064] The first spring valve 114a is disposed between the valve spool122 and a shoulder provided by the adjustment ring 78 threadinglyinserted in threads 80 formed in the housing 126 proximate to the inletport 132. In addition, a valve stem 140 is threadingly coupled to thevalve spool 122. A radiused end 142 of the valve stem 140 is axiallypositioned by the nose plate 56 of differential rolling diaphragm 54 inresponse to motions of the plunger 32. The first and second springvalves 114 a and 114 b are configured such that the first spring valve114 a has a higher value of axial force than the second spring valve 114b throughout their range of motion in order to guarantee forciblecontact between the valve stem 140, nose plate 56 and plunger 32.Substantially force balanced operation is provided by selected values ofplunger force opposed by differential compressive force from the firstand second spring valves 114 a and 114 b through their range of axialpositions. In practice this is accomplished by modulating electricalcurrent flowing through the solenoid 36 according to known current toplunger force conversion values.

[0065] Similarly to the two-way flow control valve 10, the plungercartridge 34 is directly mounted in a back plate 146 and the coil 42 ismounted upon the plunger cartridge 34 and then urged into contact withthe back plate 146 by the retaining nut 44. In this case however, theadjustment ring 78 is axially adjusted such that a selected sum of axialopening values of the first and second round edged helical orifices 118a and 118 b is achieved. The threaded near end 148 of the valve stem 140is elongated in order to facilitate axial manipulation of the valvespool 122 during this assembly operation. As with the two-way flowcontrol valve 10, the adjustment ring 78 is then staked in position.Then the proportional solenoid 36 is axially positioned a selected smalldistance from its internal closed physical stop (not shown) and theaxial position of the valve stem 140 is adjusted such that the firstround edged helical orifice 118 a is closed. Finally, a lock nut 150 isutilized to lock the valve stem 140 in place.

[0066] Thus, the first and second round edged helical orifices 118 a and118 b can be counter modulated in size between the first round edgedhelical orifice 118 a being nominally closed and the second round edgedhelical orifice 118 b being open as effected when the proportionalsolenoid 36 is fully energized; and the first round edged helicalorifice 118 a being open at a minimal proportional solenoid force valuewhereat the differential force provided by the first and second springvalves 114 a and 114 b substantially closes the second round edgedhelical orifice 118 b.

[0067] As depicted in the partially schematic sectional view presentedin FIG. 2A, the improved low flow impedance three-way flow control valve110 of the present invention is intended for use in selectivelydistributing engine coolant flow between a radiator bypass line 152connected to its second output port 128 b and leading to the inlet port90 of the centrifugal pump 92, and a radiator input line 144 connectedto its first output port 128 a and leading to an input fitting 154 onthe radiator 86. In addition, the input line 88 returning coolant comingfrom the radiator 86 is also connected to the inlet port 90 of thecentrifugal pump 92. As before, coolant issuing from centrifugal pump 92flows through the engine 98 and on to the inlet port 132 of thethree-way flow control valve 110. As depicted in all of FIGS. 1, 2A and2B, the inlet ports 18 and 132 are optimized for direct attachment to aboss (not shown) on the engine 98.

[0068] The improved low flow impedance two- and three-way flow controlvalves 10 and 110 provide inherently fail-safe operation because eitherof the spring valve 12 or the combination of spring valves 114 a and 114b urge respective valve spools 28 and 122 toward the nose plate 56 andplunger 32. Should the solenoid 36 or its drive fail, all coolant wouldbe directed to the radiator 86.

[0069] As depicted in FIG. 4 however, if it is desired to utilize animproved two-way valve 160 in conjunction with the bypass line 94, thepreviously described fail-safe function must be inverted. Generally,such an inclusive bypass assembly would be used in conjunction with atwo-way flow control valve 10 controlling coolant flow to the radiator86. Because the proper fail-safe condition is for all coolant to flowthrough the radiator, it is clear that the fail-safe condition for thetwo-way valve 160 is for that valve to close rather than open. Thus thetwo-way valve 160 could be termed a normally closed two-way valve. Inany case, this problem is readily solved by utilizing the improved lowflow impedance three-way valve 110 with output flow from the firstradially oriented output passage 116 a blocked by the simple expedientof not providing a first output port 128 a in a modified housing 162.Then the failsafe condition is implemented by stopping electricalcurrent flow to the proportional solenoid 36.

[0070] A primary advantage of using improved low impedance two- andthree-way flow control valves of the present invention in place ofpresent thermostats is that engine temperature may be intelligentlycontrolled. For instance, an engine can be operated at elevatedtemperatures during part throttle operation and then cooled wheneverincreased power levels are demanded. Because of more efficient engineoperation thus obtained, it has been estimated that fuel economy may beimproved by as much as 2%. As depicted in FIG. 2B however, more completeintelligent cooling can be provided if the centrifugal pump 92 isreplaced by driven by a purpose built centrifugal pump 156 driven by anelectric motor 158. In that case, coolant flow can be matched to actualengine cooling demand. And in addition, because of greatly reducedengine accessory drive loading, this can result in truly meaningfulimprovement in overall operating efficiency and improvements in fueleconomy approaching 4%.

[0071] In order to minimize the load on the electric motor 158, it isimportant to keep pressure drop through the associated improved two- orthree-way flow control valve 10 or 110 to a minimum. At the same time,it is desirable to minimize both stoke length and hydraulically sourcedaxial loading for the comprised valve spool 28 or 122. In addition, itis also desirable to eliminate position feedback for the valve spool.Further, because of the lack of Coulomb friction it is possible toeliminate position feedback for the valve spool 28 or 122.

[0072] These goals are all accomplished in two- and three-way flowcontrol valves 10 and 110 because the spring valves 12, 114 a and 114 beffect flow metering via closure of the round edged helical orifices 82,118 and 118 b, respectively, rather than via closure of sharp edgedorifices. As a result, no vena contractas are formed with respect tofluid flow through the round edged helical orifices 82, 118 and 118 b.This results in minimal flow resistance and the absence of axial forcecomponents for spring valves 12, 114 a and 114 b. The deleteriouseffects of Coulomb friction are also avoided because none of the rollingdiaphragm 48, differential rolling diaphragm 54, or spring valves 12,114 a and 114 b comprise sliding valve elements. All of these factorscombine to result in minimal size and drive power for the proportionalsolenoids 36. These factors have been enabled by a new method ofselective flow metering comprising closure of the round edged helicalorifices 82, 118 and 118 b formed between the coils of spring valves 12,114 a and 114 b.

[0073] As depicted in FIG. 5 then, the new method for selective flowmetering comprises the steps of: providing a fluid flow path whereinsubstantially all fluid to be selectively metered flows radially througha round edged helical orifice formed between coils of a spring valve;and reducing or increasing the size of that round edged helical orificeby respectively compressing or allowing axial expansion of the springvalve.

[0074] As mentioned above however, it has been found difficult toreliably regulate differential fluid flow between the radiator 86 andradiator bypass line 152 as a function of valve spool position. Again,this is because the flow impedance of each of the first and second roundedged helical orifices 118 a and 118 b is similar to or even lower thanthe load impedance presented by either the radiator 86 or radiatorbypass line 152. In addition, it is felt that it may prove necessary toperiodically clear debris from the round edged helical orifices 82, 118a and 118 b.

[0075] Both of these problems can easily be resolved according to a newmethod of operating any of the improved low flow impedance flow controlvalves 10, 110 and 160 as a “bang-bang” servo wherein in the case of aflow control valve comprising a single round edged helical orifice thatorifice is continually cycled between fully open and closed positions inlow frequency pulse width modulated fashion, or in the case of a flowcontrol valve comprising more than one orifice those orifices arealternately continually cycled between fully open and closed positionsin low frequency pulse width modulated fashion. In the later case forinstance, the regulation of differential fluid flow between the radiator86 and radiator bypass line 152 via the improved low flow impedancethree-way flow control valve 110 is accomplished by directly controllingthe fraction of time when all engine coolant flow passes through theradiator 86 vs. the remaining fraction of time when all engine coolantflow passes through the radiator bypass line 152.

[0076] In general as is depicted in FIG. 6, the new method ofcontrolling low impedance flow control valves comprises: providing atleast one interruptible fluid flow path between a source and aselectable destination of fluid flow; providing means for substantiallyinterrupting fluid flow through a single such fluid flow path oralternately through either of multiple such fluid flow paths; andcontinually cycling the means for substantially interrupting fluid flowin a low frequency pulse width modulated fashion.

[0077] Utilizing the new method of controlling low impedance flowcontrol valves depicted in FIG. 6 also eliminates the requirement forthe solenoid 36 to be a proportional solenoid. Since control is binaryin nature, non-proportional solenoid 36′ must satisfy only tworequirements. Firstly, it must generate enough force to move the valvespools 28 and 122. Secondly once in its activated position, it mustcontinue to generate enough holding force to maintain activation. Thissimplifies the selection process for choosing the solenoid 36′ and hasthe potential to reduce average electrical power requirements.

[0078] Depicted in FIG. 7 is circuit 170 whereby electrical power isdelivered to the solenoid 36′ from a battery 172 via buss 174, nodes 176and 178, and FET 180. During initial turn-on, the FET 180 is fullyturned on thereby accelerating current through solenoid inductance 182and resistance 184. After initial turn-on, the FET 180 is pulse widthmodulated as required to complete and maintain activation of thesolenoid 36′ by providing sufficient average voltage values across thesolenoid resistance 184. During the time periods when the FET 180 is inan off state, solenoid current is delivered from the node 178 back tothe node 176 via a free-wheeling diode 186.

[0079] With reference now to FIGS. 8 and 9, thereshown in respectivesectional and partially schematic isometric views is improved low flowimpedance three-way flow control valve assembly 190. Traditional in-linedesign wherein a proportional solenoid is utilized to directly drive avalve spool is not required because of the selfcentering nature ofspring valves. In the three-way flow control valve assembly 190 a pairof oppositely directed first and second two-way spring valves 192 a and192 b is mechanically coupled via a lever 194 and respectively utilizedfor selectively fluidly coupling a central flow distribution port 196 toa first generally annular output passage 198 and to a second generallyannular output passage 200. In turn, the first output passage 198fluidly communicates with a radiator output port 202 and the secondoutput passage 200 fluidly communicates with a bypass passage 204.

[0080] The new method of controlling low impedance flow control valvesenables the three-way flow control valve assembly 190 to be operated ina bang-bang servo mode. This obviates any requirement for a proportionalsolenoid whereby a simple linkage-coupled pull-type solenoid 206 isutilized to drive the lever 194. The first two-way spring valve 192 autilizes a stronger first spring 208 a than a second spring 208 butilized in the second two-way spring valve 192 b. This results in afail safe mode wherein all coolant flowing from the central flowdistribution port 196 goes to the radiator output port 202.

[0081] The first and second two-way spring valves 192 a and 192 b areradially disposed with reference to the central flow distribution port196. Each two-way spring valve 192 a and 192 b functions generally as apoppet valve that is sealed from a back chamber 210 by a rollingdiaphragm 212 juxtaposed between a valve head 214 and a valve piston216. The outer periphery of each of the rolling diaphragms 212 isretained by a cylinder ring 218 and a circular push-on retaining ring220 against a shoulder 222 formed in housing 224.

[0082] The valve pistons 216 are axially located by first and second camfollowers 226 a and 226 b mounted on the lever 194. The lever 194 isactuated by the pull-type solenoid 206 against the differential forceprovided by the first and second springs 208 a and 208 b. Reasonablepart tolerances are accommodated by configuring the first and second camfollowers 226 a and 226 b with respective first and second eccentricstuds 228 a and 228 b. During assembly, the first spring 208 a is fullycompressed and the first eccentric stud 228 a is adjusted and locked ina position such that the plunger 230 of pull-type solenoid 206 is notquite at its outward stop position. After the first spring 208 a isallowed to extend and compress the second spring 208 b the secondeccentric stud 228 b is adjusted and locked in a position such that theoverall travel distance of the lever 194 is properly attained. Then thebody 232 of the pull-type solenoid 206 is mounted on cover 234 and thatassembly is positioned over the plunger 230 and secured by bolts (notshown).

[0083] As most clearly shown in FIG. 9, the improved low flow impedancethreeway flow control valve assembly 190 is fully integrated with acentrifugal pump 236 whereby outgoing coolant flow is directed towardradiator 86 via radiator output port 202 and returning coolant flowcoming from the radiator is received via inlet port 90. Bypassed coolantflow is directed to an input chamber 238 of the centrifugal pump 236 viathe bypass passage 204. As depicted in FIG. 9, the housing 224 combinesthe various elements of the three-way flow control valve assembly 190and the centrifugal pump 236 including pump scroll 240 and the bypasspassage 204. The housing 224 can be directly mounted to the engine 98via either or both mounting flanges 242 if desired. The centrifugal pump236 can be driven either by an electric motor 244 as shown or by anengine accessory drive belt (not shown).

[0084] With reference now to FIG. 10, thereshown in a sectional view isimproved low flow impedance three-way flow control valve assembly 250.Three-way flow control valve assembly 250 is an alternate low flowimpedance three-way flow control valve assembly comprising first andsecond mechanical metering edges 252 a and 252 b in place of the firstand second spring valves 192 a and 192 b. It is generally constructedaccording to the above described architecture of three-way flow controlvalve assembly 190 and utilizes many of the same parts. In this casehowever, valve heads 254 serve directly in forming the metering edges252 a and 252 b, in addition, first and second valve pistons 256 a and256 b are formed as extended portions of lever 258. Further, the valveheads 254 are fixedly attached to the first and second valve pistons 256a and 256 b by bolts 260 and thus directly to the lever 258. The lever258 acts against a dedicated return spring 262 that is located above thesecond valve piston 256 b by a boss 264 and compressed between thesecond valve piston 256 b and a bracket 266. The return spring 262applies closing force to the second valve piston 256 b and is therebyutilized for urging the valve heads 254 and the solenoid plunger 230toward their fail safe positions.

[0085] Because of the curvilinear motion of the lever 258 resulting fromits motion about pivot point 268, it is necessary to locate the pivotpoint 268 in a nominally coplanar manner with the rolling diaphragms 212in order to avoid lateral distortion thereof as a byproduct of levermotion. This results in a lateral component in the closing motion of thevalve heads 254. Moreover as shown in the half open position depicted inFIG. 10, the curvilinear motion results in the orifices formed by thefirst and second mechanical metering edges 252 a and 252 b beinggenerally wedge shaped. Also, there is no provision for accommodatingmechanical tolerances in the three-way flow control valve assembly 250.This may require selective assembly whereby, for instance, a lengthgraduated selection of links 270 may be required to position the body232 of the pull-type solenoid 206 in a sufficiently accurate manner.

[0086] Having described the invention, however, many modificationsthereto will become immediately apparent to those skilled in the art towhich it pertains, without deviation from the spirit of the invention.Such modifications fall within the scope of the invention.

Industrial Applicability

[0087] The improved low flow impedance two-way and three-way flowcontrol valves 10, 110, and 160, and three-way flow control valveassemblies 190 and 250 are optimized for selectively controllingautomotive engine heated coolant flow to a host vehicle's radiatorand/or a bypass line, and thus for optimizing engine operatingconditions. It is believed that this will serve to improve fuel economyand because of that it is further believed that the technology will findwide spread commercial usage.

1. An improved low flow impedance flow control valve of the type havinga housing, an inlet port, an output passage, and an axially moving valvespool, wherein the improvement comprises: spring valve means capturedbetween the valve spool and a shoulder of the housing for selectivelymetering a flow of fluid from the inlet port to the output passage via around edged helical orifice formed between the open coils of the springvalve as a function of the instant axial position of the valve spool andthe differential pressure therebetween.
 2. An improved low flowimpedance two-way flow control valve of the type having a housing, anaxially oriented inlet port located within a first end of the housing,an annularly oriented output passage disposed within the housingproximate to a first end thereof, and an axially moving valve spool,wherein the improvement comprises: spring valve means captured betweenthe valve spool and a shoulder located within the first end of thehousing for selectively metering a flow of fluid from the inlet port tothe output passage via a round edged helical orifice formed between theopen coils of the spring valve as a function of the instant axialposition of the valve spool and the differential pressure therebetween.3. The improved low flow impedance two-way flow control valve of claim 2additionally comprising: a rolling diaphragm located proximate to thesecond end of the housing for fluidly isolating the output passage froma back chamber formed behind the valve spool and constraining the valvespool for axial movement within the housing.
 4. The improved low flowimpedance two-way flow control valve of claim 3, wherein the improvementfurther comprises: a solenoid provided for axially positioning the valvespool; at least one pressure balancing port formed in the valve spoolfor conveying fluid from the inlet port to the otherwise nominallysealed back chamber for balancing fluid pressure values on either sideof the valve spool; a differential rolling diaphragm located proximateto the solenoid for fluidly isolating the plunger cartridge of thesolenoid from fluid generally present within the back chamber; and theshoulder being configured as part of an axially adjustable ring forpositioning the shoulder such that the round edged helical orifice ofthe spring valve is substantially closed when the solenoid is fullyenergized.
 5. An improved low flow impedance three-way flow controlvalve of the type having a housing; an axially oriented inlet portlocated in a first end of the housing; first and second annularlyoriented output passages disposed within the housing and fluidlyisolated one from another by a central housing bulkhead, the firstannularly oriented output passage being located proximate to a first endof the housing and the second annularly oriented output passage beinglocated proximate to the second end of the housing; and an axiallymoving valve spool, the valve spool being positioned by a valve stem andincluding an axially oriented flow channel, wherein the improvementcomprises: a rolling diaphragm located proximate to the central housingbulkhead for fluidly isolating the output passages one from another andconstraining the valve spool for axial movement within the housing;first spring valve means captured between the valve spool and a shoulderlocated within the first end of the housing for selectively metering aflow of fluid from the inlet port to the first output passage via around edged helical orifice formed between the open coils of the firstspring valve as a function of the instant axial position of the valvespool and the differential pressure therebetween; and second springvalve means captured between the valve spool and the second end of thehousing for selectively metering a flow of fluid from the inlet port tothe second output passage via the flow channel and a round edged helicalorifice formed between the open coils of the second spring valve as afunction of the instant axial position of the valve spool and thedifferential pressure therebetween.
 6. The improved low flow impedancethree-way flow control valve of claim 5, wherein the improvement furthercomprises: a solenoid for axially positioning the valve stem and valvespool; a dominant one of the spring valve means being configured withstronger compression force than the other spring valve means for urgingthe valve stem in a direction opposing the solenoid; a differentialrolling diaphragm located proximate to the solenoid for fluidlyisolating the plunger cartridge of the solenoid from fluid generallypresent within the three-way flow control valve; the shoulder beingconfigured as part of an axially adjustable ring for positioning theshoulder such that a selected sum of axial opening values of the firstand second round edged helical orifices is achieved; and means foradjustably attaching the valve stem to the valve spool for relativeaxial positioning thereof, after the axially adjustable ring has beenproperly positioned, such that the round edged helical orifice of thedominant spring valve is substantially closed when the solenoid is fillyenergized.
 7. The improved low flow impedance three-way flow controlvalve of claim 5, wherein output flow from a dominant one of the springvalve means is blocked via not providing an output port therefore so asto reconfigure the improved low flow impedance three-way flow controlvalve of claim 5 as a normally closed two-way valve.
 8. A method forselective flow metering, wherein the method comprises the steps of:providing a fluid flow path wherein substantially all fluid to beselectively metered flows radially through a round edged helical orificeformed between coils of a spring valve; and reducing or increasing thesize of that round edged helical orifice by respectively compressing orallowing axial expansion of the spring valve.
 9. A method of controllinglow impedance flow control valves, wherein the method comprises thesteps of: providing at least one interruptible fluid flow path to a likenumbered output port or ports from an input port; providing means forsubstantially interrupting fluid flow through a single such fluid flowpath or alternately through multiple such fluid flow paths; andcontinually cycling the means for substantially interrupting fluid flowin a low frequency pulse width modulated fashion.
 10. An improved lowflow impedance three-way flow control valve assembly, comprising: firstand second coupled and oppositely directed two-way valves; respectivefirst and second generally annularly oriented output passages forreceiving selectively apportioned fluid flow from the first and secondtwo-way valves; means for mechanically coupling and physicallypositioning the first and second two-way valves; and means formechanically driving the means for mechanically coupling and physicallypositioning.
 11. The improved low flow impedance three-way flow controlvalve of claim 10 wherein the means for mechanically coupling andphysically positioning is a lever.
 12. The improved low flow impedancethree-way flow control valve of claim 10, additionally comprising:two-way spring valve means utilized for the first and second coupled andoppositely directed two-way valves; a solenoid utilized as the means formechanically driving; respective first and second valve heads foractuating the springs comprised in the spring valves; and respectivefirst and second rolling diaphragms for fluidly isolating themechanically coupling and physically positioning and solenoid from thefluid.
 13. The improved low flow impedance three-way flow control valveof claim 12 wherein the one of the two-way spring valve means opposingthe solenoid is configured with stronger compression force than theother spring valve means for urging the means for mechanically couplingand physically positioning in a direction opposing the solenoid.
 14. Theimproved low flow impedance three-way flow control valve of claim 10,additionally comprising: mechanical metering edges utilized for thefirst and second coupled and oppositely directed two-way valves; asolenoid utilized as the means for mechanically driving; respectivefirst and second valve heads mechanically coupled to the lever andcomprising the mechanical metering edges; and respective first andsecond rolling diaphragms for fluidly isolating the mechanicallycoupling and physically positioning and solenoid from the fluid.
 15. Thelow flow impedance three-way flow control valve assembly of claim 10,additionally comprising a centrifugal pump, wherein the valve assemblyand its associated flow passages are housed and included along with thecentrifugal pump and a bypass passage for fluidly coupling the secondoutput passage of the three-way flow control valve assembly with aninput chamber of the centrifugal pump within a common housing.